Influence of lung volume, fluid and capillary recruitment during positional changes and exercise on thoracic impedance in heart failure

Chul Ho Kim, Matthew A. Fuglestad, Maile L.Ceridon Richert, Win K. Shen, Bruce D. Johnson

Research output: Contribution to journalArticle

2 Scopus citations


It is unclear how dynamic changes in pulmonary-capillary blood volume (Vc), alveolar lung volume (derived from end-inspiratory lung volume, EILV) and interstitial fluid (ratio of alveolar capillary membrane conductance and pulmonary capillary blood volume, Dm/Vc) influence lung impedance (ZT). The purpose of this study was to investigate if positional change and exercise result in increased EILV, Vc and/or lung interstitial fluid, and if ZT tracks these variables. Methods: 12 heart failure (HF) patients underwent measurements (ZT, EILV, Vc/Dm) at rest in the upright and supine positions, during exercise and into recovery. Inspiratory capacity was obtained to provide consistent measures of EILV while assessing ZT. Results: ZT increased with lung volume during slow vital capacity maneuvers (p<0.05). Positional change (upright→supine) resulted in an increased ZT (p<0.01), while Vc increased and EILV and Dm/Vc decreased (p<0.05). Moreover, during exercise Vc and EILV increased and Dm/Vc decreased (p<0.05), whereas, ZT did not change significantly (p>0.05). Conclusion: Impedance appears sensitive to changes in lung volume and body position which appear to generally overwhelm small acute changes in lung fluid when assed dynamically at rest or during exercise.

Original languageEnglish (US)
Pages (from-to)75-81
Number of pages7
JournalRespiratory Physiology and Neurobiology
StatePublished - Oct 1 2014



  • Fluid accumulation
  • Heart failure
  • Lung impedance

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology
  • Pulmonary and Respiratory Medicine

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